The molecular and genetic distances and relations between enzyme and ribosomal protein-controlling regions of pneumococcal DNA will be studied. The genes available in various arrays in this region include ribosome modifying streptomycin and erythromycin resistance markers, a gene controlling mannitol phosphate dehydrogenase, and several allelic factors modifying a folic acid synthetase to produce sulfonamide resistance. A portion of the sulfonamide marker region can be present as a tandem duplication with various heterozygotic gene arrangements. All these genes are measured quantitatively by DNA transformation of pneumococci with intact DNA or fractions obtained by restriction endonuclease hydrolysis and fractionation. The relation of the right and left portions of the sulfonamide resistance region to each other and to their neighboring genes is studied in normal DNA and in that bearing the tandem duplication.